Freezer device

ABSTRACT

A refrigeration apparatus includes two sub passages which are branched from a main passage located between a condenser and an expansion part and which are connected to a compressor. On the sub passages are provided supercooling-use expansion parts, and supercooling-use heat exchangers for performing heat exchange between a refrigerant on an outlet side of the supercooling-use expansion part and a refrigerant of the main passage. Therefore, each time the refrigerant of the main passage passes through the two supercooling-use heat exchangers the degree of liquid supercooling of the refrigerant is increased.

BACKGROUND OF THE INVENTION

The present invention relates to a refrigeration apparatus in which, forexample, a compressor, a condenser, an expansion part and an evaporatorare connected to one another.

In a conventional refrigeration apparatus, a compressor, a condenser, anexpansion valve and an evaporator are connected to one another in aloop, where a supercooling-use heat exchanger is placed between thecondenser and the expansion valve. Then, a liquid refrigerant derivedfrom the condenser is branched into two flows. One flow of the liquidrefrigerant makes a main flow liquid, while the other flow of the liquidrefrigerant, after passing through the supercooling-use heat exchanger,super-cools the main flow liquid via the supercooling-use heatexchanger, then being led to the compression chamber of the compressor(see JP H11-248264 A, patent document 1).

However, the prior art refrigeration apparatus is incapable of furtherincreasing the degree of liquid supercooling of the refrigerantimmediately before the expansion valve. Thus, there have beenlimitations in improving the refrigerating capacity and energyefficiency (COP).

Patent document 1: JP H11-248264 A, FIG. 1

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide arefrigeration apparatus which is capable of further increasing thedegree of liquid supercooling of the refrigerant immediately before theexpansion part, thus enabled to improve the refrigerating capacity andenergy efficiency (COP).

In order to achieve the objects, the refrigeration apparatus includes:

a compressor;

a condenser;

an expansion part; and

an evaporator,

wherein the compressor, the condenser, the expansion part and theevaporator are connected to one another in order,

the refrigeration apparatus further includes:

at least two sub passages which are branched from a main passage locatedbetween the condenser and the expansion part and which are connected tothe compressor;

supercooling-use expansion parts provided on the sub passages,respectively; and

supercooling-use heat exchangers for performing heat exchange between arefrigerant on an outlet side of the supercooling-use expansion part anda refrigerant of the main passage.

In this refrigeration apparatus of the invention, since thesupercooling-use heat exchanger is provided at least two in number alongthe main passage, the degree of liquid supercooling (SC) can beincreased each time the refrigerant of the main passage passes throughthe plurality of supercooling-use heat exchangers.

That is, since the refrigeration apparatus of this invention has aso-called three- or more-stage expansion economizer cycle, the degree ofliquid supercooling of the refrigerant immediately before the expansionpart can be further increased so that the refrigerating capacity andenergy efficiency (COP) can be further improved, as compared withprior-art refrigeration apparatuses having a two-stage expansioneconomizer cycle.

Moreover, in the refrigeration apparatus of one embodiment, thecompressor is a single screw compressor including a screw rotor and apair of gate rotors which mesh with the screw rotor so as to sandwichthe screw rotor from both sides, and the sub passages are provided twoin number,

one of the sub passages being connected to one side of a boundarydefined by the pair of gate rotors, and the other of the sub passagesbeing connected to the other side of the boundary defined by the pair ofgate rotors.

In the refrigeration apparatus of this one embodiment, since the subpassage and the supercooling-use heat exchanger are provided two innumber, an economizer cycle can be applied to each of compression spacesdivided by an boundary defined by the pair of gate rotors in thecompressor. Thus, a so-called three-stage expansion economizer cyclebecomes applicable, so that performance improvement can be achieved.

Moreover, in the refrigeration apparatus of one embodiment, therefrigeration apparatus includes:

a discharge-side supercooling control section for detecting temperatureand pressure of the refrigerant on the discharge side of the compressorand, based on a result of the detection, performing control of anopening degree of the supercooling-use expansion part in one of the subpassages; and

a suction-side supercooling control section for detecting temperatureand pressure of the refrigerant on the suction side of the compressor inthe other sub passage and, based on a result of the detection,performing control of an opening degree of the supercooling-useexpansion part in the other sub passage.

In the refrigeration apparatus of this one embodiment, since one of thesupercooling-use expansion parts is controlled by the discharge-sidesupercooling control section while the other supercooling-use expansionpart is controlled by the suction-side supercooling control section, thetwo supercooling-use expansion parts can be controlled based ondifferent temperatures and pressures, respectively.

Consequently, in the two supercooling-use expansion parts, hunting ofthe opening and closing operations due to control exerted based on acommon temperature and pressure can be avoided so that a stable coolingeffect can be obtained.

According to the refrigeration apparatus of the present invention, sincethe supercooling-use heat exchanger is provided at least two in numberalong the main passage, the degree of liquid supercooling of therefrigerant immediately before the expansion part can be increased sothat the refrigerating capacity and energy efficiency can be improved.

Also, according to the refrigeration apparatus of one embodiment, sincethe economizer cycle is applied to each of the divisional compressionspaces of the compressor, performance improvement can be achieved.

Also, according to the refrigeration apparatus of one embodiment, sincethe two supercooling-use expansion parts are controlled based ondifferent temperatures and pressures, respectively, competition of theopening and closing operations between the two supercooling-useexpansion parts can be prevented so that a stable cooling effect can beobtained.

BRIEF DESCRIPTION OF THE-DRAWINGS

FIG. 1 is a simplified configurational view showing an embodiment of therefrigeration apparatus of the present invention;

FIG. 2 is a PH diagram for comparison between the refrigerationapparatus of the invention and a refrigeration apparatus of a prior art;and

FIG. 3 is a flowchart showing the control of a discharge-sidesupercooling control section and a suction-side supercooling controlsection.

REFERENCE NUMERALS

-   1 a compressor-   1 a a screw rotor-   1 b a gate rotor-   2 a condenser-   3 an expansion part-   4 an evaporator-   10 a main passage-   11 a sub passage-   12 a supercooling-use expansion part-   13 a supercooling-use heat exchanger-   14 a discharge-side supercooling control section-   15 a suction-side supercooling control section

DETAILED DESCRIPTION OF THE INVENTION

Hereinbelow, the present invention will be described in detail byembodiments thereof illustrated in the accompanying drawings.

FIG. 1 shows a simplified configurational view showing an embodiment ofthe refrigeration apparatus of the invention. In this refrigerationapparatus, a compressor 1, a condenser 2, an expansion part 3 and anevaporator 4 are connected to one another in a loop, constituting arefrigeration cycle using a refrigerant.

This refrigeration cycle is explained. A vapor phase refrigerantdischarged by the compressor 1 has its heat absorbed in the condenser 2,resulting in a liquid phase state. The resulting liquid phaserefrigerant is decompressed by the expansion part 3, resulting in atwo-phase state of vapor phase and liquid phase. Thereafter, thetwo-phase refrigerant (wet gas) has heat imparted in the evaporator 4,resulting in a vapor phase state. The resulting vapor phase refrigerantis sucked and pressurized in the compressor 1, and then discharged inthe compressor 1 again.

As the compressor 1, for example, a single screw compressor is used. Inmore detail, the compressor 1 includes a screw rotor 1 a, and a pair ofgate rotors 1 b, 1 b which meshes with the screw rotor 1 a so as tosandwich the same from both sides. Meshing between a thread groove ofthe screw rotor 1 a and tooth portions of the one pair of gate rotors 1b, 1 b defines the compression chamber, and the refrigerant iscompressed to high pressure in the compression chamber.

The condenser 2 includes a fan 7, and the refrigerant is cooled by aircooling of the fan 7. The expansion part 3 is given by using, forexample, an electronically controlled expansion valve or a capillarytube. The evaporator 4 is given by using, for example, a heat exchangerfor cooling water (liquid heat transfer medium) by the refrigerant.

Moreover, this refrigeration apparatus has two sub passages 11, 11 whichare branched from a main passage 10 between the condenser 2 and theexpansion part 3 and connected to the compressor 1. It is noted that themain passage 10 and the sub passages 11 are implemented by piping.

More specifically, by the branch from upstream and downstream sides ofthe main passage 10, an upstream-side sub passage 11 and adownstream-side sub passage 11 are formed. This upstream-side subpassage 11 is connected to one side of the pair of gate rotors 1 b, 1 b,which are assumed as a boundary, while the downstream-side sub passage11 is connected to the other side of the pair of gate rotors 1 b, 1 bassumed as the boundary. That is, the upstream-side sub passage 11communicates with a midway portion of the compression chamber located onone side of the boundary given by the pair of gate rotors 1 b, 1 b,while the downstream-side sub passage 11 communicates with a midwayportion of the compression chamber located on the other side of theboundary given by the pair of gate rotors 1 b, 1 b.

Further, a supercooling-use expansion part 12 and a supercooling-useheat exchanger 13 for performing heat exchange between the refrigeranton the outlet side of the supercooling-use expansion part 12 and therefrigerant of the main passage 10 are provided on each of these subpassages 11.

More specifically, an upstream-side supercooling-use heat exchanger(higher-stage economizer) 13 and a downstream-side supercooling-use heatexchanger (lower-stage economizer) 13 are set along the main passage 10.In FIG. 1, although the sub passages 11 are branched from the mainpassage 10 on the downstream side of the supercooling-use heat exchanger13, yet those sub passages 11 may also be branched from the main passage10 on the upstream side of the supercooling-use heat exchanger 13.

Next, operation of the two supercooling-use heat exchangers 13, 13 isexplained. The liquid phase refrigerant in the main passage 10, comingfrom the condenser 2, is first diverged to the upstream-side sub passage11. This liquid phase refrigerant in the upstream-side sub passage 11 isdecompressed by the supercooling-use expansion part 12, resulting in atwo-phase refrigerant of vapor phase and liquid phase. The resultingtwo-phase refrigerant absorbs heat from the liquid phase refrigerant ofthe main passage 10 via the upstream-side supercooling-use heatexchanger 13, resulting in a vapor phase refrigerant. The resultingvapor phase refrigerant is sucked into the compressor 1. In thisprocess, the liquid phase refrigerant in the main passage 10 is cooledvia the upstream-side supercooling-use heat exchanger 13.

Thereafter, the cooled liquid phase refrigerant in the main passage 10is diverged to the downstream-side sub passage 11. The liquid phaserefrigerant in the downstream-side sub passage 11 is decompressed in thesupercooling-use expansion part 12, resulting in a two-phase refrigerantof vapor phase and liquid phase. The resulting two-phase refrigerantabsorbs heat from the liquid phase refrigerant of the main passage 10via the downstream-side supercooling-use heat exchanger 13, resulting ina vapor phase refrigerant. The resulting vapor phase refrigerant issucked into the compressor 1. In this process, the liquid phaserefrigerant in the main passage 10 is cooled via the downstream-sidesupercooling-use heat exchanger 13.

According to the refrigeration apparatus having the above-describedconstruction, since the two supercooling-use heat exchangers 13, 13 areprovided, the refrigerant of the main passage 10 can be increased in thedegree of liquid supercooling each time it passes through the twosupercooling-use heat exchangers 13, 13.

That is, the refrigeration apparatus of this invention, by virtue of itshaving a three-stage expansion economizer cycle made up of the threeexpansion parts 3, 12, 12 and the two supercooling-use heat exchangers13, 13, can be increased in the degree of liquid supercooling for therefrigerant immediately before the expansion part 3, thus capable offurther improving the refrigerating capacity and energy efficiency(COP), as compared with the prior-art refrigeration apparatus having atwo-stage expansion economizer cycle made up of two expansion valves andone supercooling-use heat exchanger.

More specifically, as shown in FIG. 2, in the refrigeration apparatus ofthe invention (three-stage expansion) indicated by solid line, thedegree of liquid supercooling (SC) is increased by the upstream-sidesupercooling-use heat exchanger (upper stage of three-stage expansionECO) and the downstream-side supercooling-use heat exchanger (lowerstage of three-stage expansion ECO) so that the refrigerating capacityis improved, as compared with the refrigeration apparatus of the priorart (two-stage expansion) indicated by broken line.

Moreover, the refrigeration apparatus of the invention, as shown in FIG.1, further includes a discharge-side supercooling control section 14 fordetecting temperature and pressure of the refrigerant on the dischargeside of the compressor 1 and, based on a result of the detection,performing control of the opening degree of the supercooling-useexpansion part 12 in the downstream, and a suction-side supercoolingcontrol section 15 for detecting temperature and pressure of therefrigerant on the suction side of the compressor 1 in the upstream-sidesub passage 11 and, based on a result of the detection, performingcontrol of the opening degree of the supercooling-use expansion part 12in the upstream.

More specifically, the discharge-side supercooling control section 14performs the opening degree control by calculating a present-timecurrent SH value from a temperature and a high-pressure pressure valueof the refrigerant within discharge piping of the compressor 1 and thencomparing the obtained value with a previously set target SH value. Thesuction-side supercooling control section 15 performs the opening degreecontrol by calculating a present-time current SH value from atemperature and a pressure value of the refrigerant within outlet pipingof the upstream-side supercooling-use heat exchangers 13 and thencomparing the obtained value with a previously set target SH value. Itis noted here that the SH value refers to a degree of superheat, whichis a temperature showing a difference from the temperature of asaturated state.

The supercooling-use expansion part 12 is provided by using atemperature-sensitive expansion valve, thus allowing its price to belowered as compared with the electronic expansion valve. Of course, anelectronic expansion valve may also be used as the supercooling-useexpansion part 12.

Next, referring to FIG. 3, operations of the discharge-side supercoolingcontrol section 14 and the suction-side supercooling control section 15are explained.

First, control operation by the discharge-side supercooling controlsection 14 is described. As the control operation starts (S101), it isdecided whether or not the current SH value (B) is greater than thetarget SH value (A) (S102). If it is greater, the control section 14opens the downstream-side temperature-sensitive expansion valve 12(S103). Conversely, if it is not greater, it is decided whether or notthe current SH value (B) is smaller than the target SH value (A) (S104).Then, if it is smaller, the control section 14 closes thedownstream-side temperature-sensitive expansion valve 12 (S105).Conversely, if it is not smaller, the control section 14 does notperform any operation for the downstream-side temperature-sensitiveexpansion valve 12 (S106).

Next, control operation by the suction-side supercooling control section15 is described. As the control operation starts (S201), it is decidedwhether or not the current SH value (D) is greater than the target SHvalue (C) (S202). If it is greater, the control section 15 opens theupstream-side temperature-sensitive expansion valve 12 (S203).Conversely, if it is not greater, it is decided whether or not thecurrent SH value (D) is smaller than the target SH value (C) (S204).Then, if it is smaller, the control section 15 closes the upstream-sidetemperature-sensitive expansion valve 12 (S205). Conversely, if it isnot smaller, the control section 15 does not perform any operation forthe upstream-side temperature-sensitive expansion valve 12 (S206).

As shown above, the downstream-side supercooling-use expansion part 12is controlled by the discharge-side supercooling control section 14,while the upstream-side supercooling-use expansion part 12 is controlledby the suction-side supercooling control section 15. Therefore, the twosupercooling-use expansion parts 12, 12 can be controlled based ondifferent temperatures and pressures, respectively.

Thus, in the two supercooling-use expansion parts 12, 12, hunting of theopening and closing operations due to control exerted based on a commontemperature and pressure can be avoided so that a stable cooling effectcan be obtained. For instance, in a case where the two supercooling-useexpansion parts 12, 12 are controlled by the discharge-side supercoolingcontrol section 14, the two supercooling-use expansion parts 12, 12 arecontrolled by a common pressure and temperature, so that the opening andclosing operations may undergo occurrence of hunting, where a stablecooling effect could no be obtained.

Without being limited to the above-described embodiment, the presentinvention may be subject to design changes within the scope of theinvention unless they depart therefrom. It is also possible, forexample, that upstream-side supercooling-use expansion part 12 iscontrolled by the discharge-side supercooling control section 14 whilethe downstream-side supercooling-use expansion part 12 is controlled bythe suction-side supercooling control section 15 additionally providedon the downstream-side sub passage 11. Also, the sub passage 11, thesupercooling-use expansion part 12 and the supercooling-use heatexchanger 13 may be provided each three or more in number, in which caseone supercooling-use expansion part 12 is controlled by thedischarge-side supercooling control section 14, and the othersupercooling-use expansion parts 12 are controlled by the suction-sidesupercooling control sections 15 provided on the sub passages 11,respectively.

1. A refrigeration apparatus comprising: a compressor; a condenseroperatively connected to the compressor; an expansion part operativelyconnected to the condenser; an evaporator operatively connected betweenthe expansion part and the compressor, the compressor, the condenser,the expansion part and the evaporator being connected to one another ina loop; a plurality of sub passages branched from a main passage locatedbetween the condenser and the expansion part and connected to thecompressor; a plurality of supercooling-use expansion parts with eachone of the supercooling-use expansion parts being provided on one of thesub passages; and a plurality of supercooling-use heat exchangers witheach one of the supercooling-use heat exchangers performing heatexchange between refrigerant on an outlet side of the supercooling-useexpansion part and refrigerant of the main passage.
 2. The refrigerationapparatus as claimed in claim 1, wherein the compressor is a singlescrew compressor including a screw rotor and two gate rotors which meshwith the screw rotor so as to sandwich the screw rotor from both sides,and a first one of the sub passages being connected to one side of aboundary defined by the gate rotors, and a second one of the subpassages being connected to another side of the boundary defined by thegate rotors.
 3. The refrigeration apparatus as claimed in claim 2,further comprising a discharge-side supercooling control sectionconfigured to detect temperature and pressure of a refrigerant on adischarge side of the compressor and control an opening degree of thesupercooling-use expansion part in the first one of the sub passagesbased on the detection; and a suction-side supercooling control sectionconfigured to detect temperature and pressure of a refrigerant on asuction side of the compressor in the second one of the sub passages andcontrol an opening degree of the supercooling-use expansion part in thesecond one of the sub passages.